Manitoba Insect Update

August 24, 2009

To report observations of insect activity or control
that may be of interest or importance to others in Manitoba, please
send messages to the above contact addresses.

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immediately when new Manitoba Insect Updates are posted, please
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John Gavloski at the address or numbers listed above.

Summary

Grasshoppers are of concern in localized areas. Levels of
soybean aphids have increased, but remain well below the
economic threshold.

Recent Insect Concerns and Observations

Grasshoppers: Some localized high populations of grasshoppers
continue to be of concern . Reports from the past week include
high populations being noted in canola, and in flax in eastern
Manitoba.

One of the questions from the past week was what options are
available to control high grasshopper populations in swathed
canola, or other swathed crops. The answer is nothing, which is
why it is important to be checking grasshopper levels earlier in
the season. If we use canola as an example, the shortest
preharvest interval for any insecticide used to control
grasshoppers or any other insect on canola is 7 days. The
preharvest interval is the number of days that must pass between
the last application of a pesticide and the cutting of the crop.
So it is the time that must pass before the crop can be swathed,
not the time until combining (except for direct-combining). So
insecticides can not be applied to a swathed crop, and in the
case of canola cannot be applied within 7 days of swathing.

Soybean aphid update: Soybean aphid levels have increased in
some fields, but are still not approaching economic levels. Some
fields have patches where the aphids are quite noticeable on the
plants, but overall the fields are well below the economic
threshold, which is when there are at least 250 aphids per plant
on average, and the population is still increasing, and the
plants are in the beginning bloom to beginning seed growth
stages.

Sunflower Insect Update: Populations of insects that feed on
sunflower seeds are generally relatively low. Data from the
pheromone-baited traps for banded sunflower moth show that
weekly counts continue to increase in most areas, indicating
that emergence and flight are still building or peaking. Counts
have generally been higher so far in traps further west in the
province, than traps in more eastern areas. Highest cumulative
counts so far are from fields near Waskada (517), Glenwood
(471), Treherne (352) and Altona (324). There have been no
reports of seed weevils at concerning levels; in most fields
they are hard to find at all.

Preventing stored grain insects: A reminder before moving and
storing new grain to clean old grain out of bins, augers,
combines, truck beds, and other areas where grain or grain
debris may be. Infestations of stored grain insects such as
rusty grain beetles do not get started by harvesting the insects
along with the grain. They are the result of insects already
being present in bins or equipment used to move grain, or
insects being able to get into the stored grain through openings
in bins or storage structures. Below is a picture of a sawtoothed grain beetle (top right), red flour beetle (bottom
left), and rusty grain beetle (bottom right) with a grain of
wheat (top left) to give perspective on size.

Stored Grain Insects

Surveys and Forecasts

Grasshopper Survey: A reminder to farm production advisors
and others involved in the grasshopper survey, that this should
be completed by the end of August. Grasshopper populations are
estimated in August, when egg-laying is normally occurring, to
determine the risk for grasshoppers damaging crops the following
year. Factors such as temperature and rainfall are accounted for
when the forecast is written. A reminder that if grasshopper
levels are high it is not possible to get exact counts as
grasshoppers jump through the vegetation as you approach.
Estimates are all that is required, and in many cases all that
is possible, for the survey.